The present embodiments relate to generating a spatially resolved magnetic resonance dataset using a coil arrangement.
When recording magnetic resonance data, one or a plurality of coils are used as transmission and receiving devices. In the case of transmission, a B1 field is emitted.
In connection with MR measurements, B1 radiofrequency fields or B1 fields are also known as high frequency pulses or HF pulses. These are used to deflect the magnetization of the examination object from the resting position by a desired flip angle. For this purpose, one or a plurality of transmission coils is/are supplied with current.
The flip angle achieved is dependent on the duration of the HF pulse and on the pulse profile. An interaction exists here between the B1 field of the high frequency pulse and the tissue that is being examined. As a result of this, the magnetization is deflected.
Even when the same coil is used for transmission and receiving, different B1 fields may be present due to different connections for transmission and receiving. When transmitting, the B1+ field is present, and when receiving, the B1− field is present.
The distribution of the B1 field of a high frequency pulse may be shown by a B1 map. This may be created for each of the fields (e.g., for the B1+ field and the B1− field).
The use, as a point of departure, of B1+ maps (e.g., B1 maps) is known for homogenizing high frequency pulses such that the distribution of the B1+ field is as homogeneous as possible in the case of transmission.
Despite these correction measures, in breast imaging, for example, artifacts often occur. For example, there may be differences in brightness in the image within breasts of a subject or between the two breasts, which occur, for example, in the form of eddy currents induced in the tissues that have been recorded. Ultimately, the signal intensities shown in the images do not correspond with the distribution in the tissue.
Methods for B1 shimming are known from US 2013/0165768, US 2013/0229176 A1, and US 2013/0021033 A1.